Diversion Berm

[1stTimeBridgeDesign]

I need to design a diversion berm, which is basically a retaining wall at the end of a drainage channel to make sure water goes into a drainage pipe. In the case of the 100yr storm, it acts as a weir and has a 4' x 1.5' cutout in the middle of the retaining wall. There is a 3 to 1 slope leading up to the wall with riprap.

My question is: When designing the diversion berm structure like a retaining wall, what is the force of the water on the wall for the 100 yr flow. It will be flowing over so would it be the static force plus a dynamic effect based on the flow? How do I calculate the dynamic force on the wall?
Thanks

 

[cvg]

make sure this is not considered a floodwall. Even if you call it a diversion berm, you may want to design it to meet FEMA requirements for floodwall, especially if your project will ever be submitted to FEMA for review.

I don't believe FEMA would require adding the shear force and even if you do add it, it is not that high. However, stability analysis of the wall should be done and you may want to make some conservative assumptions such as:

- scoured down to the footing or to the calculated scour depth

- saturated soil behind the wall

- rapid drawdown with saturated backfill conditions

- FEMA freeboard requirements

the following engineering manual may help in your design:

USACE, EM 1110-2-2502, 29 September 1989, Retaining and Flood Walls